The Giant Magnets In the ITER Fusion Reactor Weigh Almost As Much as a Boeing 747

Nuclear fusion reactors are no joke. Sure, we haven't made one that works well enough to actually generate usable energy, but even these very early models are enormous, complex feats of sophisticated engineering. A fun detail about the ITER reactor—currently being built in France—is that the magnets it requires are absolutely gigantic. So gigantic, they weigh almost as much as a plane.

The ITER reactor—a joint project between the European Union, India, Japan, China, Russia, South Korea, and the United States—is a relatively straightforward "Tokamak" design. Straightforward compared to the nightmarish tangle of a stellarator, anyway. These donut shaped devices attempt to coax a ring of superheated plasma into being inside themselves, using giant magnets to create a field that holds it in place; there's not much else that can hold this sort of plasma in place.

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Pulling this off is difficult for a whole host of reasons but before you can even try, you need your magnets in place. In the ITER's case, these magnets are giant D-shaped rings, 46 feet high, 30 feet wide, and 3 feet thick. It weighs in at roughly 120 tons, which Engineering and Technology Magazine notes is roughly the weight of a 747, though it's worth noting that would be a completely empty 747, and the plane would still have 10 or 20 tons on this ring.

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This magnet is just part of the reactor's first Toroidal Field coil, of which it will need a full eighteen before it can actually go into operation. Construction is slated to be completed in 2019, with plasma experiments starting in 2020, and full-on fusion tests by 2027.